X-IRRADIATED CNS OF THE SYRIAN HAMSTER 



273 



Fig. 14. Cerebral cortex, 218 hr after exposure to 7,500 r showing perinuclear 

 region of a reactive astrocyte. The cytoplasm contains many fine fibrils (Fi). N, nu- 

 cleus. X 21,600. 



alterations that might be specific for ionizing radiation. With our present 

 knowledge, it is not possible to be dogmatic about the significance of observa- 

 tions which, though the result of examining many himdreds of microphoto- 

 graphs, still are based on alterations in only a relatively small number of cells 

 from limited areas. Nonetheless, it appears that in areas of necrosis following 

 x-radiation there is a depression of phagocytic elements in number and 

 activity. Thus, from areas of total traumatic necrosis, the macrophages are 

 filled with vacuoles and inclusions, while in regions of correspondingly com- 

 plete x-ray induced necrosis, the phagocytes aie fewer and their phagocytic 

 function less prominent. 



It is possible that ionizing radiation affects the ability of macrophages to 

 proliferate in and around a necrotic area, as well as altering the enzymes 

 involved in the breakdown of phagocytosed material. 



